Question: Which of these numbers is composite? ${5,\ 7,\ 19,\ 63,\ 71}$
A composite number is a number that has more than two factors (including 1 and itself). 5, 7, 19, and 71 each have only two factors. The factors of 63 are 1, 3, 7, 9, 21, and 63. Thus, 63 is the composite number.